Tracking fluid displacement along a wellbore using real time temperature measurements. A method of tracking fluid displacement along a wellbore includes the steps of: monitoring temperature in real time in the wellbore; and observing in real time a variation in temperature gradient between fluid compositions in the wellbore. Another method of tracking fluid displacement along a wellbore includes the steps of: monitoring temperature along the wellbore; and observing a variation in temperature gradient due to a chemical reaction in the wellbore. Another method includes the step of causing a variation in temperature gradient in the fluid while the fluid flows in the wellbore.